Process of making multiform rubber thread



April 22, 1941. R. G. JAMES arm. 2,238,885

PROCESS OF MAKING MULT IFORM RUBBER THREAD Filed May 10, 1938 JIE OBEET cu ibjifs ATTORN EY Patented Apr. 22, 1941 PROCESS OF MAKING MULTIFORM RUBBER THREAD Robert Gilbert James and Sydney Frederick Smith, Wylde Green Birmingham, England,

assignors to Dunlop Rubber Company Limited,

London, England,

a British company Application May 10, 1938, Serial No. 206,998 In Great Britain July 16, 1937 5 Claims. (01. 18--54) Our invention relates to a process for the production of rubber thread having three or more filaments integrally or closely united without twisting or braiding so that the length of the final thread is substantially the same as the individual filaments, and the invention relates more particularly to a method or process whereby the filaments are arranged in a compact, symmetrical grouping in which, for example, each filament is in contact with at least two other filaments.

In the production of multi-filament thread from filaments formed by the extrusion of rubber latex through separate nozzles into a liquid coagulant or the like difiiculties are encountered which hinder or prevent the formation by mere juxtaposition of a thread with the filaments in a regular, compact grouping. For example, when a three-filament thread is to be made, the filaments may arrange themselves as a fiat braid, or

as a right angle triangle, and not in the more compact form of an equilateral triangle.

Our present invention obviates these difiiculties and provides a method or process in which the several filaments arrange themselves through natural forces into the by mere juxtaposition.

In our invention three or more filaments of an aqueous dispersion of rubber or similar material are formed by extruding thin streams of latex upwardly through a liquid coagulant and then drawing a selected group of three or more threads upwardly through the surface of the liquid, and thence away. In drawing the filaments upwardly through the surface of the liquid the surface tension about the threads tends to crowd them into the most compact formation, it being a characteristic of the surfaces of liquids to tend to contract in such a way as to reduce the surface. Accordingly, when the filaments as, for example, three of them, are drawn upwardly in slightly spaced position, the surface of the liquid drawn up with the filaments and enclosing them tends to contract in much the same manner as a stretched membrane and, therefore, draws the filaments, which are freely movable within the liquid, together in. a compact structure. Inasmuch as the filaments are free to move in the liquid and as the surface most compact grouping tension of the liquid surrounding the filaments as they leave the water is directed inwardly toward the center of the strand being formed, the filaments move into the most compact arrangement.

In the case of a' three-filament thread, the

three filaments will arrange themselves in a trefoil cross section, as this is the arrangement that occupies the least space. As the number of filaaments increases the configuration or grouping of the filaments each changes accordingly and will assume a more nearly rounded or circular outline in cross section. Also, the surface tension of the liquid tends to draw the filaments into close contact so that they will remain in the configuration that is imposed upon them as they leave the surface of the liquid.

In the accompanying drawing the invention is illustrated by way of example as applied to the formation of a three-filament thread, Fig. 1 showing diagrammatically and on a greatly enlarged scale an apparatus whereby the filaments are extruded upwardly into and drawn upwardly out of a coagulating bath. Fig. 2 is a. horizontal section taken on line 2--2 of Fig. 1, and Fig. 3 is a horizontal section on a still larger scale taken on line 3-3 of Fig. 1.

In the apparatus illustrated in the accompanying drawing the filaments are extruded from orifices If] in the top plate I l of an extruding head l2 supplied with the latex or aqueous dispersion through the supply pipe l3. This dispersion or latex may be either the natural latex obtained from India rubber trees, or of balata or guttapercha trees, or it may be an artificial latex or dispersion formed from rubber, gutta-percha, balata or similar vegetable resins, or from artificial or synthetic resins either vulcanized or unvulcanized, and may comprise such materials as reclaim or waste. All of these materials are designated as latex or dispersion. These materials may comprise concentrates such as are obtained in U. S. Patent 1,848,164, or English Patents Nos. 290,313 and 219,632, to which may be added any one or more of the usual compounding ingredients.

The thin streams of latex or dispersion of any of the above types passing through the orifices It in spaced relation flow into and pass or are drawn upwardly through a bath M of coagulating liquid. During the upward passage of the latex streams they are coagulated or otherwise transformed more or less completely into filaments l5 which are then drawn through the surface of the liquid and over a pulley or other drawing means l6. As the filaments l5 pass through the surface of the bath 14, they draw upwardly a film of liquid shown at I I in Fig. 2. The surface tension of this liquid acts to contract the resultant structure and draw the filaments with equal force toward the center until they meet in a symmetrical trefoil arrangement. The filaments will then unite more or less intimately, depending upon the extent of coagulation and the condition of the surface of the film.

In the specific embodiment shown the drawing roll i6 is illustrated as being directly above the orifices ill so as to draw the thread vertically. It will be understood that while this is preferred, a deviation from the vertical is permissible provided the deviation is not sufiiciently great as to distort the forces of surface tension acting as shown in Fig. 2. For example, if the filaments move horizontally, the direction of tension would be different and might be such as to draw the filaments into a flat ribbon shape, or into some other unsymmetrical arrangement. It will be understood that after the threads pass over the rollers I6, they may pass through other processing treatments as, for example, further coagulation, or drying, or dehydrating, etc., or they may be merely washed and dried, or stretched. The completed threads may be vulcanized after completion.

It will be understood that more than three filaments may be employed and drawn into a single thread, or that threads made up of filaments may similarly be drawn into a compact structure without twisting. Generally, for symmetrical appearance, it is desirable for the individual filaments :to be of the same gauge, color and type of compound. It is, however, possible to employ combinations of filaments of different gauges, types and colors inasmuch as the surface tension will in each case act to give the most compact assembly of filaments. It will be understood, of course, that instead of using a single drawing head i2, a number of heads, each having one or more orifices, may be employed. Also, while a coagulant bath has been illustrated by way of example, it is to be understood that this designation will include liquid media which bring about the solidification of rubber latex, not only by coagulation of a specific type, but may include gelling and dehydration.

Our invention is very economical in plant over methods heretofore used for, by replacing each single nozzle by a group of nozzle capillaries, the same number of multi-form threads can be made as was heretofore possible with single filament threads. For example, a plant or plant unit running 120 ends of single thread may, by our invention, run with equal facility 120 ends of multi-form thread.

What we claim is:

1. A method of forming and uniting more than two freshly coagulated rubber filaments into a compact grouping to form a thread which com prises continuously drawing a group of more than two of said filaments in free suspension below the surface of a liquid upwardly through said surface and out of said liquid at substantially a right angle to said surface into a group arranged regularly and compactly about an axis of symmetry whereby said filaments are drawn together and brought into close contact by the surface tension of said liquid as they are drawn from its surface.

2. A method of forming and uniting more than two freshly coagulated rubber filaments into a compact grouping to form a thread which comprises extruding an aqueous dispersion of rubber composition into a setting bath to form sepa rate freely suspended movable filaments and drawing a group of more than two of said filaments in free suspension below the surface of a liquid upwardly through said surface and out of said liquid at substantially a right angle to said surface into a group arranged regularly and compactly about an axis of symmetry whereby said filaments are drawn together and brought into close contact by the surface tension of said liquid as they are drawn from its surface.

' 3. A method of uniting more than two freshly coagulated rubber filaments into a compact grouping to form a thread which comprises continuously drawing a group of more than two of said filaments'in free suspension below the surface of a liquid upwardly through said surface and out of said liquid at an, angle to provide a substantially symmetrical surface tension about said filaments and into a group arranged regularly and compactly about an axis ofsymmetry whereby said filaments are drawn together and rought into close contact by the surface tension of said liquid as they are drawn from its surface.

4. A method of forming a compact untwisted thread of more than two rubber filaments from an aqueous dispersion of rubber composition which comprises extruding said aqueous dispersion through a number of orifices of filamentary dimensions upwardly into a bath of liquid to fix and set thestreams of dispersion issuing through said orifices to substantially solid filamentsin free suspension below the surface of said bath of liquid and drawing a group of more than two of said filaments upwardly through said surface and out of said liquid at substantially a right angle tosaid surface into a group arranged regularly and compactly about an axis of symmetry whereby said filaments aredrawin together and brought into close contact by the surface tension of said liquid as they are drawn from its surface.

5. A method for the production of rubber thread of three or more filaments integrally united in a compact group without twisting or braiding, which comprises extruding a number of latex'filaments at a common speed into a liquid setting bath and in a'freely suspended condition in said setting bath, drawing a group of more than two of the coagulated' filaments vertically out of the coagulant through the upper surface thereof and into a group arranged regularly and compactly about an axis of symmetry and suificiently close to be, drawn into intimate contact and compact arrangement by the surface tension of said setting bath as they pass through the surface thereof. 7

ROBERT GILBERT JAMES. SYDNEY FREDERICK SMITH. 

